Automatic vacuum system



Sept. 19, 1950 P. c. sMlTH 2,522,969

AUTOMATIC VACUUM SYSTEM 4 Sheets-Sheet 1 @i W @L 2. @g Z Filed Nov. 28, 1947 m lNvi-:NTOR

VFERRY E. SMITH 7a fuerza/y GUN o@ unitair/:Nr BY 2 l n Z ,4Z ATTORNEY Sept' 19, 1950 P. c. SMITH 2,522,969

AUTOMATIC VACUUM SYSTEM Filed Nov.28, 1947 4 Sheets-Sheet 2 @Wa p Z @Pie/Irf- Pif-Paw "la/1o "Pei-PUMP" "opffrf ai@ f' n-li?, i `lNvEm-orz FERRYDSMITH ATTORNEY Sept.` 19, 1950 Filed Nov. 28, 1947 P. c. SMITH 2,522,969

vAUTOMATIC VACUUM SYSTEM 4 Sheets-Sheet 3 Sw FERRY E. SMITH ATTORNEY Sept. 19, 1950 P. c. SMITH 2,522,959

AUTOMATIC VACUUM SYSTEM Filed Nov. 28, 1947 4 sheets-sheet 4 INVENTOR Fam-WE. Sg 1TH BY I ATTORNEY Patented Sept. 19, 1950 Perry 0. Smith, Moorestown, N. J., assignor to Radio Corporation of Americana corporation .0f Delaware Appliance November 2s, 1947, serial No. 785,542

This invention relates to apparatus for automatically controlling vacuum pumping systems and, more particularly, to apparatus for automatically controlling systems having both a fore pump for low vacuum and a diiusion pump for high vacuum. In general, there are two diiierent types of apparatus utilizing chambers requiring the use of vacuum pumping systems for obtaining high vacuum conditions therein. One of these types is exemplified by the vacuum tube which comprises a sealed chamber containing a number of electrodes. Usually, the chamber is exhausted to a very high vacuum and permanently sealed so that thev interior is never again exposed to the atmosphere during the life of the tube. The second type, which is exemplified by the specimen charnber of an electron microscope, also requires the obtaining of a very high vacuum but is frequently opened to the atmosphere for loading and unloading during its lifetime. This type needs 'a vacuum pumping system of a high degree of efnciency and dependability in order to keep it in proper working condition. Although the control system of the present invention may be used with `either of these two types of equipment, it has particular advantages when used with the second type.` y

In any vacuum pumping system, for exhausting gases from a vacuum chamber, which includes both a fore or roughing pump and a diffusion pump, the use of four main valves represents optimum requirements. One of these valves is in the `line connecting the intake of the fore pump tothe outlet of the dii-fusion pump. A vsecond is in the line connecting the vacuum Vchamber to the intake of the fore pump, a third `is" in the line connecting the intake of the diffusion pumpto the vacuum chamber and a fourth is in the passageway leading from the vacuum chamber to the atmosphere. In previous Vacuum systems, such as used in electron microscopes or highvacuurn evaporationapparatus, these valves have'been operated manually. This requires close attention on the part of the operator and diligence in making certain that the right lvalve is closed before others are opened, and vice versa.

Another type of manual control upon which the systemv of the present invention is an improvementvis the use of a valve block containing all the valves used in the equipment and la system of gears and cams lcontrolled `by a crank lever 4for advancing the system through valious operating steps. In this type of prior art system, the turning of the control crank results in accomplish'in'gthe valving operations which accompany the particular operation being carried out With the equipment. Thus, in an electron microscope, for example,there are four positions of the crank correspondingto loading pre-pump, operate and neutraL This type, although an `adv-ance over systems requiring individual control,"by the operator, of each separate valve, still requires the constant attendance and close attention of an operator who must constantly observeivarius gauges and meters in order to operate the crank at the proper times.

In any of these previously used manual systems oicontrol,` there are serious disadvantages, other than wasted operators time, which the system of the present invention avoids. For example, in manual systems, there is always present the hazardrof incorrect valving sequence. This cannot occur in the rautomatic control system of the present invention. In manual systems, which all depend to some extent on the judgment of the operator as to what is `the proper time for manipulating the valves for the next step of the cycle, there `is much lost `timewhen the operating vacuum'might be utilized for carrying out the work operation. Another great disadvantage in the manual' and mechanically operated systems previously'employed lies in the inefliciency of the vacuum seals which are commonly employed in connection with operating rods and levers which extend through the Walls of the vacuum cham-.- ber. There have usually been employed Sylphon bellows, which are very thin exible brass tubes subject to failure, due to fatigue and corrosion, -particulally at the soldered junctions. Other improved seals including rubber grommets have .been substituted for the Sylphcn bellows but these require the use of a great dealr of power to move the control rods extending through the rubber seals. In the automatic system of the present invention, electrically operated solenoid valves, having nol such disadvantages, may be employed.

The principal object,'then, of the present invention is to provide a vacuum pumping control system which isffully automatic.

Anotherobject of the invention is to provide an improved vacuum control system which may be applied to any equipment having an evacuable chamber which must frequently be opened to the Another object of the present invention is to provide an automatic system for controlling the operation of valves in a plurality of vacuum systems by a single operator.

Still another object of the present invention is to provide an improved automatically controlled evacuating system for maintaining the pressure within a vacuum chamber at a desired level.

Other objects of the invention will be apparent and the invention will be more readily understood from a reading of the following specification. including the accompanying drawings, of which:

Fig. 1 is a block diagram showing the arrangement of the principal valves in relation to the main components of a typical vacuum system with which the present invention may be used;

Fig. 2 is a block diagram indicating circuits connecting various parts of a control system constructed in accordance with the present invention;

Figs. 3a, 3b and 3c are diagrammatic cross sectional views of a typical vacuum chamber showing valve positions for different operating conditions;

Fig. 4a is a wiing diagram including the relays and valve solenoids showing the positions of the valve pistons and relay contacts with all relays and solenoids at rest or de-energized in a system constructed in accordance with the present invention;

Figs. 4b. 4c and 4d are similar wiring diagrams showingr relav contact positions and valve piston positions during different portions of a complete operations cycle;

' Fig. 5 is a diagram showing conditions of electrical current in relation to valve operation timiner present during each part of a complete cycle of operation of a typical system constructed in accordance with the present invention;

Fig. 6 is a block diagram of another embodiment of the system shown in Fig. 2. and

Fig. '7 is a detail diagram of part of the circuit indicated more generally in Fig. 2 and Fig. 6.

Referring now to the drawings. a typical embodiment of the invention will be described in connection with the evacuation. to a high degrec, of a vacuum chamber which may be the column of an electron microscope. although it obviously could be any other piece of eouipment in which it was desired to obtain a condition of high vacuum.

In a typical system. -as shown in Fig. l, there may be an evacuable chamber 2 to which is connected an outlet passage 4 having a three-way opening 6. To one of these openings, there is connected the intake of a diffusion pump 8 through a passageway IU. A valve C for maintaining the passageway I0 in a closed or open condition, as desired, is positioned therein. To another of the openings. there is connected the intake of a fore or roughing pump I2 by means of a passageway I4. The passageway I4 has a valve B positioned therein. The outlet of the diffusion pump 8 is connected to the intake passageway I4 of the fore pump I2 through a passageway I6, the connection into the passageway I4 being located between the pump I2 Iand valve B. The passageway I6 also has in it a valve A. The third opening to the vacuum chamber 2 is connected through a passageway I8, having a valve D positioned therein. to the atmosphere. preferably through a lter dryer 20.

In a typical cycle of operation of the system, as applied to an electron microscope, for exam-n ple, including the valves, shown in Fig. 1, the valves may be opened and closed in proper sequence by a system of the general type shown inFig. 2.

The complete system may comprise, in general, a vacuum pumping unit comprising a diiusion pump 8 Vand a roughing pump I2 which is designed to evacuate the vacuum chamber 2 to a desired degree of vacuum and maintain the vacuum as long as desired. The roughing pump is operated by a motor associated therewith. The vacuum system also includes a number of solenoid-operated valves, indicated generally at 22, which are controlled through the operation of a relay system 23 connected to the solenoid valves through the circuit indicated generally at 24.

The relay system is, in turn, partially controlled by the operator pressing the start switch 35 and the release switch 3l connected to the relay system through circuits 29 and 3G, respectively. The relays also operate automatically in response to information received from the thermogage 32, through circuit 39.

A power supply 4B supplies D.C. power to the relay system through circuits indicated generally at 48 in Fig. k2 and having connections more particularly shown in Figs. la-4d. The power supply i6 also supplies D.C. power to the solenoid system indicated generally at 22 in Figs. 2 and 6, through circuits indicated generally at 50. The solenoid power connections are also illustrated in detail in Figs. Llat-4d.

The system further provides for turning the high voltage supply to the electron gun 26 on and ofi automatically in response to information received from the ionization gage, preferably by the switching means described in U. S. Patent 2,383,600 and for preventing the high voltage from being connected to the electron gun except when the pressure within the vacuum chamber has been reduced to the proper value, by means more particularly illustrated in Fig. 7.

A more specic embodiment of that part of the invention which includes the automatic operation of the vacuum system valves indicated in Fig. 1 will now be described with reference to Figs. 3a to 3c and Figs. 4a to 4d.

Referring first to Figs. 1 and 3a to 3c, the vacuum system is assumed to be in load condition (Fig. 3a) with the vacuum chamber 2 open to the atmosphere as for the insertion of a new specimen. Both pumps have previously been turned on and remain on throughout the operations. In the load condition, the valves are positioned, as shown in Fig. 3a, with valves A and D open and valves B and C closed. The fore pump I2 continuously pumps the diiusion pump 8. The operator then initiates an operations cycle by pressing a starting button 36. The apparatus rst assumes the condition designated as pre-pump (Fig. 3b). Valves A and D close, after which valve B opens, valve C remaining closed. Thus, the passageway to the atmosphere is sealed 01T and the fore pump I2 switches from pumping the diffusion pump and begins to rough pump the vacuum chamber 2. At the same time, the diffusion pump 8 is held at low pressure due to the fact that valves A and C are closed.

When a certain pressure; i. e., about 10 microns of mercury, has been attained within the vacuum chamber 2, which pressure is indicated by a thermogage 32 in the fore pump line, another part of the cycle designated operate (Fig. 3c) automatically begins. For this part of the cycle, Valve B closes and. D remains closed. Valves A 2. The closing of contacts C open after valve `B is closed. This results in the forefpump |2 no longerbeing directly conchamber 2 due to the opening of valve C. 'Both pumps are thus connected tothe vacuum cham` ber in series. y I p Withl both pumps .evacuating the vacuum chamber in series, the pressure within the chamber isreduced to a value required forcertain operations within the chamber. In `the case of an electron microscope, this may be 5 x l0*4 mm. of

Lmercury. The low pressure readinglis indicated,

preferably, on an ionization type gage `34 connected to the chamber 2.

When the operateV cycle is completed, the` apparatus may be returned to the load position, by the operator pressing release Vswitch 31, with the valves in the position described previously in connection with this partof the cycle and shown in Fig. 3a. o'

In order to accomplish the above cycle in a completely automatic manner, a novel system, forming an important part of thepresent invention, has been devised and one embodiment is shown schematically in Figs. 4a to 4d.

Fig. 4a illustrates the positionsl of the various relay contacts and valve pistons of this embodi ment when no current isV iiowing in any of the relay coils or valve solenoids.l In the relay |00, which controls the solenoid of valve A, contacts a, b and c are open, while contacts d and e are closed. In the relay |02 which controls the solenoid of valve B, .the single contact a is open. In the relay |04, which is energized in response to information received from the thermogage .33, contacts e and c are open while contactsmb and d are normally closed. In the'relay |06, which controls the solenoid of valve C, the single con,- tact a is closed. In the relay |08 which is ener-` gized bythe releaseswitch `3l, the contacts a, b and c are open while contact-d is closed. In the relay I I0, which controls the solenoid ofl valve D;

` both contacts a and b are open. .When anyof these relays is energized, its contacts assume po` sitions opposite to those indicated above.

It is also apparent, as illustrated in Fig. 4a, that when no current is flowing in any ofthe valve solenoids, valves A and C are open while valves B yand D are closed. I

When initiating acycle` of operations, a momentary impulse is given the :relay |00 by the` 1. Relay |00 is energized, closing its contacts"rali` and c and opening its contacts d and c.. ,1t locks closed by being connected .tothe power supply 46, through the closedcontactslMa of unenergized relay |04 and through its own closed power contacts |00e.` ,p

,l energizes `the solenoid 38 of valve A, thereby closing the valve A, which Iis between the `:fore pump 2Wand diiusion pump 8. ,I 3. The closing of contacts |00e applies power through the closed contactsulll'lllb Vof rJunenerw-g gized relay |04 to energize the delayed-action relay |02. The closing of lcontacts` |02@ pf. re;

before the opening of valve B, contacts |00d of relay |00,'which are connected through contacts ||0a, breaks the power connection to the solenoid 42 of valve D, even though the contacts |`|0a of relay 0 may still be closed. This de-'ene'rgize's solenoid 42 of Valve D and closes the valve, thus disconnecting the vacuum chamber 2 from the atmosphere. (The valve D is adapted to close when its solenoid is de- 4energized.) The opening of contacts I00d, which are connected through a second path to contacts |00a, also removes locking current for relay |00 through its contacts |08a, thus deenergizing relay |08. The de-energizing of relay |08 opens contacts |08c which are connected Ato one side Jof relay ||0, thus de-energizingrelay H0.

5. The opening of contacts |00e of relay |00, which'are connected to contacts ||0b, also opens the locking current path to relay I0.

Through the occurrence of all of the above described operations, the pre-pump part of a cycle has' been initiated.

Pre-pumping continues until the pressure within the vacuum chamber 2 is low enough to support the diiusion pump. When this point is reached, further solenoid valve switching takes place. This is accomplished as a result of impulses supplied by thefthermogage portion 32 of the vacuum gage system. The thermogage32 comprises a thermocouple located in the passage between the fore pump I2 and valve B. As the pressure is decreased, the energy radiated by the hotthermocuple is decreased, its temperature is increased, and the thcrmoelectric voltage through the thermocouple is increased.

When the circuit of thermogage 32 produces a current equivalent to that of a pressure of approximately |0 microns of mercury, a relay 33 associated therewith is actuated, closing contacts 35 which closes a power circuit energizing relay 1. Contacts |040 close; thus relay |04 locks itself through contacts |04c, in series with the closed contacts |08d of de-energized relay |08, these two pairs of contacts being connected.

2. Contacts |04d are opened, thereby opening the circuit through contacts |02c, and thereby breaking the power circuit through solenoid 40 and thus de-energizing this solenoid which closes valve B. At the Ysaine time, contacts |0417 are opened, de-energizing slow-operating vrelay |02, which opens the contacts |02a and, hence, also opens the circuit of the solenoid 40 of valve B. Althoughr either one or the other of these two events would appear to be unnecessary, the de-energizing of relay |02 is` undesirably slow because it is a delayed action type. Provision is therefore made for deenergizing solenoid 40 in a more rapid manner. p

3..-Contacts |04e are closed, energizing slow-operating relay |00, thereby opening contacts 1f |06a, which, in turn, de-energize's the solenoid 44 of valve C and opens this valve.

4. Contacts |04a. are opened, thereby unlocking relay and de-energizing it. This opens the contacts |0b, de-energizing the solenoid 3 8 of valve A, opening the Valve;

The above events result in the occurrence of the second or operate stepl of the cycle. VValve B closes just before valves A and C open. The

fore pump thus switches yfrom pumping Athe vacuum chamber 2 to pumping thev diffusion pump 8 now, itself, connectedto the vacuum chamber. l

With both pumps exhausting the vacuum chamber 2, a pressure is soon attained which is sufficiently low to allow the desired work operationv of the equipment tol proceed. In the case of an electron microscope, a signal light or audible sound may be given to indicate that the instrument is in operating condition. The electron gun, as well as high voltage, may `also be turned on automatically, allowing the-operator to observe a specimen chamber. As applied to other types of equipment, such as molecular evaporation apparatus, heating current may be automatically turned on in the filaments. As applied to the microscope (Fig. 2);,'the impulse which initiates these operating functions may be` supplied from a circuit, indicated generally :at 28, associated with the ionization type gage 34, which is connected to the vacuum chamber 2. This gage may be ofthe type comprisinga two element tube having a'cold cathode. passes an amount of current which depends upon the degree of ionization of the residual gas within the vacuum chamber towhich it is connected. The degree of ionization is, in turn, a function of the pressure within the chamber.

The electronic circuit for turning on high voltage current to the electron gun is preferably as shown and described in U. S. Patent 2,383,600. However, in order to prevent this circuit :from being energized while valve C is closed,'an interlock circuit, Fig. 7, is provided as part of the present invention. With thev opening of valve C, contacts 25 are closed. When thecontacts of relay 52 are also closed in response to information received from ionization gage 34, current is supplied from high voltage supply to electron gun 26 through transformers 54 and 56. (Relay 52 corresponds to relay 2| in the above mentioned Patent 2,383,600.)

When the operator has finished observing the specimen within the chamber, where the equipment being operated is an electron microscope, he presses a button temporarily closing, then releasing the release contacts 31 and thus o-perating relay |08. The operation of relay |08 produces the following events, illustrated in Fig. 4d:

The tube With the completion of the above events, the vacuum chamber 2 has been placed in condition for reloading. Valve D has been opened after Valve C has closed, thus connecting the vacuum chamber to the atmosphere. The fore pump |2 continues to pump the diffusion pump 8.

The complete cycle can now be repeated as above described and as soon as desired. However, in order to re-initiate the pre-pump portion of the cycle, additional circuit descriptions must be included.

Relay |00, on being energized by the start impulse caused by the operator pressing starting button 36, opens its contacts |00d, thereby deenergizing relay |08 by breaking the circuit through its locking contacts |08a. Upon the release of relay |08, contacts |081) open but valve C remains closed because contacts |00a remain closed. The opening of contacts |080' removes locking current from relay ||0 while, at the saine time, the opening of contacts lllld breaks the circuit through contacts llla, de-energizing solenoid 42 and closing valve D. This doubleseries contact control permits the immediate de-energizing of solenoid 42, closing valve D through operation of relay |00, thereby overcoming the slower release characteristics of relay I I0.

The pulse from the circuit controlled by thermogage 32 is continuous and relay |04 is held locked despite its own locking circuit until relay |08 is energized. The thermogage circuit is never opened, once closed, unless the pressure in the fore pump line increases to some small amount above 10 microns of mercury. This, of course, would be analogous, under normal conditions, to the point in the cycle where the system was switching from load to pre-pump.

It Will be noted that in the embodiment of the circuit operation described, the solenoids of some of the valves are energized when the valve is closed and, in others, current ows in the solenoids when the valve is opened. This is best illustrated in Fig. 5, which also shows the relative opening and closing occurrences of each valve. The reason for this apparent non-conformity is that it is desired to have no current flowing through the solenoids when the instrument is in "operate condition, in the case of an electron microscope, since stray currents of all types affect the ne focusing of the electron beam. With other types of equipment, such as evaporators. it way not matter Whether energizing of its solenoid opens or closes a particular valve.

Although the invention has been illustrated as applied to the operation of an electron microscope, it may be applied just as well to other types of vacuum equipment, either with or without further modification. For example, it may be applied to apparatus for depositing coating materials by evaporation techniques of the general type shown in U. S. Patent 2,338,234. The circuits for operating this type of system are shown diagrammatically in Fig. 6.

In operation, the operator presses a start button 58, releasing a first interval timer 59. This interval timer may be any of several conventional types Well known to the industry; having a synchronous motor with gears, shafts, cams and cam operated contacts to control various associated circuits at desired intervals. This iirst timer 59 may, rst of all, close a pair of contacts actuating a circuit 60, supplying current, causing vacuum chamber 2 to be closed off from the atmosphere as by starting a motor for lowering a bell jar in place. After the bell jar is lowered in place, the timer may then cause the closing of starting button 36 through a circuit 6l, similar to circuit 29 in Figs. y4a-4d, initiating an operations cycle of the vacuum equipment after the manner previously described.

The pumping cycle is automatically carried on, with proper valve switching as previously described under the pre-pump step, until information is received by the second interval tim- -er 62 from ionization gage 34 over circuit 63 that a suitable low pressure has been reached.

When this information is received, the second timer 62 vthen starts up, generating another series of ,pulses which may close a circuit 64, energizing either a single filament evaporating a coating material, a plurality of filaments for simultaneously evaporating a number of materials, or a number of filaments in timed sequence for applying -a plural layer coating. The valves are in the operate" position previously indicated (Fig. 4c)

Just as in the previous example, means are provided to make certain that the valve C is in open position before energization of the filaments can take place. As indicated in Fig. 7, the contacts 25 must be closed due to the opening of valve C before the circuit can be i completed through the power supply and the evaporation heater filament or filaments.

After a desired time interval, controlled by the setting of the second interval timer 62, the laments are de-energized, the release switch 31 is actuated through circuit 30 and the system returns to the load condition (Fige. 4d).

`When the heating filaments have been deenergized and the valves have returned to load condition, the second timer 62 sends an impulse to the first timer 59 over circuit 65 and the first timer again starts up. closing contacts reversing the bell jar controlling motor through circuit 60. thus raising the jar and placing the system in condition to be reloaded by the operator.

As in the previous example, pilot lights or other indicating devices may be utilized to indicate the condition of the system to the operator. The ionization gage 34 m-ay operate a pilot light 88 through a circuit 6l indicating when the operate cycle is ready to begin and how long it continues. and another pilot light 68 may be operated by the second interval timer 62 through a circuit 69 to indicate when the cycle is complete and ready for load operation.

There has thus been described a system which provides for automatic operation of either one or up to several vacuum units by a single operator. The operator need only place the system in condition for operation by loading and unloading the vacuum chamber at the proper times, if applied to a vacuum processing unit or load. observe and unload the specimen chamber, if an electron microscope. The valving operations are all carried out automatically and various other steps are also accomplished without the operator touching the equipment.

I claim as my invention:

1. A vacuum system comprising an evacuable chamber, a vacuum gage connected to said chamber. means for exhausting said chamber, said exhausting means being responsive to information supplied thereto by said gage, and means within said chamber for performing a, work operation, said work means being operative in response to information supplied thereto by said vacuum gage and by said exhausting means.

2. A system according to claim 1 in which saidv vacuum gage is an ionization type gage.

3. A system according to claim 1 in which said work means comprises an electrically energizable filament.

4. A system according to claim 1 in which said work means comprises a source of electrons.

5. A vacuum system comprising an evacuable chamber, a vacuum gage connected to said chamber, means for exhausting said chamber, said exhausting means comprising a vacuum pump, an exhaust passage connected between said chamber and said pump, and solenoid valves controlling airflow through said passage, a relay system for operating said valves, and means for operating said relay system inresponse to the condition of said vacuum gage.

6. A Vacuum system comprising an evacuable chamber, means for indicating the pressure of said chamber, means for exhausting said chamber, said (exhausting means comprising at least one vacuum pump and solenoid valves, a relay system for operating said valves, means within said chamber for performing a Work operation, and means operative in response to information received from said pressure indicating means for actuating said relay system and for actuating said work performing means.

7. A system according to claim 6 in which said work operation performing means comprises a source of electrons.

8. In a system for evacuating a vacuum chamber comprising a forepump and a diffusion pump having a passageway, including a first valve, connecting the intake of said fore pump to the outlet of said diffusion pump, a passageway, in-

cluding a second valve, connecting said fore pump to said Vacuum chamber, a passageway, including a third valve, connecting said diffusion pump to said vacuum chamber, an air intake passageway, including a fourth Valve, connecting said vacuum chamber to the atmosphere, a first relay energized by the closing of a starting switch for simultaneously closing said first and fourth valves, a second relay energized by operation of said first relay for opening said second valve a predetermined time after the closing of said first and fourth valves, a third relay energized in response to a predetermined pressure within said chamber for closing said second valve and opening said first valve, a fourth relay energized by operation of said third relay for opening said third valve. a fifth relay energized by an external source of energy for closing said third valve,

predetermined pressure within said chamber for energizing an electrical element within said chamber only when said third valve is open.

PERRY C. SMITH.

REFERENCES CITED The following references are of record in the le of this patent:

FOREIGN PATENTS Number Country Date 411,911 Great Britain June 18, 1934 

